Electromagnetic wave radiator

ABSTRACT

An electromagnetic wave radiator may include: a first metal layer; a plurality of metal side walls vertically protruding along an edge of the first metal layer; and a second metal layer suspended over the first metal layer. The second metal layer includes a plurality of ports radially extending from edges of the second metal layer and a plurality of slots penetrating the second metal layer in a radial direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 62/447,963, filed on Jan. 19, 2017, in the U.S. Patentand Trademark Office, and Korean Patent Application No. 10-2017-0033205,filed on Mar. 16, 2017, in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein in their entireties byreference.

BACKGROUND 1. Field

The present disclosure relates to an electromagnetic wave radiator, andmore particularly, to an electromagnetic wave radiator radiating acircularly-polarized millimeter-wave/terahertz (THz)-wave.

2. Description of the Related Art

A millimeter-wave is an electromagnetic wave having a wavelength ofabout 1 to about 10 millimeters and has a frequency of about 30 to about300 GHz. The millimeter-wave is used in various fields such as themilitary and automobile radars, satellite communication, and radionavigation, and is expected to be used for large-capacity voice, image,and data transmission in the next generation 5G ultra-wideband mobilecommunication network. A terahertz (THz)-wave is an electromagnetic wavehaving a frequency of about 0.3 to about 3 THz, which is used forsecurity and medical purposes, and is expected to be widely used in thefuture.

Accordingly, various devices for efficiently transmitting and receivingmillimeter-waves and THz-waves are being developed. For example, amillimeter-wave/THz-wave microstrip patch antenna has a large area and alow quality factor (Q-factor). In order to improve this issue, devicessuch as a multi-port driven antenna, a slot-ring traveling-waveradiator, and a multi-port driven antenna having a radiator core areproposed for the millimeter-wave/THz-wave. However, these devices stilldo not provide high-enough Q-factors.

SUMMARY

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented example embodiments.

According to an aspect of an example embodiment, an electromagnetic waveradiator may include: a first metal layer; a plurality of metal sidewalls vertically protruding along an edge of the first metal layer; anda second metal layer suspended over the first metal layer. The secondmetal layer may include a plurality of ports extending radially fromedges of the second metal layer and a plurality of slots penetrating thesecond metal layer in a radial direction.

Every pair of adjacent metal side walls of the plurality of metal sidewalls may be spaced apart from each other, and each port of theplurality of ports may be disposed to pass through a gap between acorresponding pair of adjacent metal side walls.

The first metal layer and the second metal layer may have an identicalregular polygonal shape. Each metal side wall of the plurality of metalside walls may be disposed perpendicular to an upper surface of thefirst metal layer at the edge of one side of the identical regularpolygonal shape of the first metal layer. A first length of the eachmetal side wall of the plurality of metal side walls may be less than asecond length of the one side of the first metal layer. A gap betweentwo adjacent metal side walls may be disposed at a vertex of theidentical regular polygonal shape of the first metal layer.

The plurality of ports may radially protrude from respective vertices ofthe identical regular polygonal shape of the second metal layer, and theplurality of slots may be disposed between a center of the second metallayer and the respective vertices of the identical regular polygonalshape of the second metal layer.

The first metal layer and the second metal layer may have an identicalcircular shape. Each metal side wall of the plurality of metal sidewalls may be disposed perpendicular to an upper surface of the firstmetal layer at the edge of the first metal layer. The edge of the firstmetal layer may correspond to a perimeter of the identical circularshape of the first metal layer. A combined length of the plurality ofmetal side walls may be less than a diameter of the identical circularshape of the first metal layer. The plurality of gaps between theplurality of metal side walls may be disposed at regular intervals alongthe perimeter of the identical circular shape of the first metal layer.

Each of the plurality of ports may protrude in the radial direction ofthe second metal layer between the plurality of gaps between theplurality of metal side walls.

The second metal layer may be in a space surrounded by the plurality ofmetal side walls.

The second metal layer may further include an opening penetratingthrough a central region of the second metal layer.

The electromagnetic wave radiator may further include at least oneoscillator configured to provide a signal to each of the plurality ofports. The at least one oscillator may be configured so that signalsprovided to the plurality of ports have an identical amplitude anddifferent phases from each other, and phase differences between signalsapplied to two adjacent ports are identical.

The second metal layer may have n ports, and a phase of the signalapplied to an m-th port may be 2mπ/n, where n is a natural number and mis 0, 1, . . . , n−1.

The at least one oscillator may be connected to the plurality of portsin a one-to-one manner.

One oscillator of the at least one oscillator may be connected to theplurality of ports via a plurality of wires and each of the plurality ofwires may have an electrical length providing a different phase delayfrom each other.

A space surrounded by the first metal layer, the plurality of metal sidewalls, and the second metal layer may define a cavity for resonance ofan electromagnetic wave, and the first metal layer, the plurality ofmetal side walls, and the second metal layer may be configured so thatthe cavity functions as a resonator, a power combiner, and a radiator.

The electromagnetic wave radiator may further include a plurality ofamplification circuits between two adjacent ports of the plurality ofports. The plurality of amplification circuits may be disposed in a loopshape between the plurality of ports.

Each of the plurality of amplification circuits may include an inputmatching unit, an inter-stage matching unit, an output matching unit, afirst common emitter transistor between the input matching unit and theinter-stage matching unit, and a second common emitter transistorbetween the inter-stage matching unit and the output matching unit.

The first common emitter transistor and the second common emittertransistor may have an identical voltage gain.

Each of the port impedances for the plurality of ports may be identicalto each other, and port admittances for the plurality of ports may beidentical to each other.

Each of the port admittances may have a negative resistance offsetting acavity load impedance at a resonant frequency, and a total admittance ofthe electromagnetic wave radiator may have a negative real part at theresonant frequency.

The electromagnetic wave radiator may be configured to radiate acircularly-polarized millimeter-wave/terahertz (THz) wave.

According to an aspect of an example embodiment, an electromagnetic waveradiator array may include a plurality of two-dimensionally arrangedelectromagnetic wave radiators. Each electromagnetic wave radiator ofthe plurality of two-dimensionally arranged electromagnetic waveradiators may include: a first metal layer; a plurality of metal sidewalls vertically protruding along an edge of the first metal layer; anda second metal layer suspended over the first metal layer, wherein thesecond metal layer includes a plurality of ports radially extending fromthe edge of the second metal layer and a plurality of slots penetratingthe second metal layer in a radial direction.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of example embodiments, takenin conjunction with the accompanying drawings in which:

FIG. 1 is an exploded perspective view of an electromagnetic waveradiator according to an example embodiment;

FIG. 2 is a perspective view of an electromagnetic wave radiator andillustrates a phase of a signal applied to each port of theelectromagnetic wave radiator according to an example embodiment;

FIG. 3 illustrates an equivalent circuit of an electromagnetic waveradiator according to an example embodiment;

FIG. 4 illustrates an equivalent circuit of a resonance circuit at oneport of the electromagnetic wave radiator;

FIG. 5 illustrates a configuration of an amplification circuit connectedbetween two adjacent ports of the electromagnetic wave radiator;

FIG. 6 is a graph illustrating frequency response characteristics of areal part and an imaginary part of the total admittance of theelectromagnetic wave radiator;

FIG. 7 is a graph illustrating a measurement result of a polarizationpattern of an electromagnetic wave radiated from the electromagneticwave radiator;

FIG. 8 is a graph illustrating a measurement result of a radiationpattern of an electromagnetic wave radiated from the electromagneticwave radiator;

FIG. 9 is a graph illustrating a measurement result of spectralcharacteristics of an electromagnetic wave radiated from theelectromagnetic wave radiator;

FIG. 10 is a graph illustrating a measurement result of phase noisecharacteristics of an electromagnetic wave radiated from theelectromagnetic wave radiator;

FIGS. 11A through 11E illustrate various example embodiments of theelectromagnetic wave radiator;

FIGS. 12A and 12B illustrate various example embodiments of a connectionrelationship between respective ports and oscillators of theelectromagnetic wave radiator; and

FIG. 13 illustrates an electromagnetic wave radiator array according toanother example embodiment.

DETAILED DESCRIPTION

In the following drawings, like reference numerals in the drawingsdenote like elements, and sizes of elements may be exaggerated forclarity and convenience. In addition, embodiments to be described beloware only exemplary and various modifications from such exampleembodiments may be possible. In the case where a position relationshipbetween two items is described with the terms “on” or “on the top of,”one item may be not only directly on the other item while being incontact with the other item but may also be on the other item withoutbeing in contact with the other item.

FIG. 1 is an exploded perspective view of an electromagnetic waveradiator according to an example embodiment. Referring to FIG. 1, anelectromagnetic wave radiator 100 according to an example embodiment mayinclude a first metal layer 110 on a semiconductor substrate 101, aplurality of side walls 120 vertically protruding along edges of thefirst metal layer 110, and a second metal layer 130 suspended over thefirst metal layer 110. The semiconductor substrate 101 may include amaterial for a general semiconductor device such as silicon or acompound semiconductor. Although not shown, a circuit for transmittingand receiving signals to and from the electromagnetic wave radiator 100may be formed on the semiconductor substrate 101. A supporting memberfor supporting the second metal layer 130 so as to be suspended withrespect to the first metal layer 110 may be arranged on thesemiconductor substrate 101.

The first metal layer 110 may be a thin and flat metal plate and bedisposed on the semiconductor substrate 101. For example, a thickness ofthe first metal layer 110 may be in a range of about 0.3 to about 0.6 μmand have a diameter in a range of about 1 to about 2 mm. In addition,the first metal layer 110 may have a circular or regular polygonalshape. In FIG. 1, the first metal layer 110 is illustrated to have aregular octagonal shape. However, the example embodiment is not limitedthereto. The first metal layer 110 may have a different shape dependingon the number of phases of signals to be coupled.

The plurality of side walls 120 may include the same conductive metal asthe first metal layer 110. When the first metal layer 110 has a regularpolygonal shape, each side wall 120 may be perpendicular to an uppersurface of the first metal layer 110 at an edge of one side of the firstmetal layer 110. For example, a height of each side wall 120 may be in arange of about 12 to about 16 μm. A width of each side wall 120 may beless than the length of one side of the first metal layer 110 so that agap may be formed between two adjacent side walls 120. For example, thegap between two adjacent side walls 120 may be at each vertex of thefirst metal layer 110. Alternatively, when the first metal layer 110 hasa circular shape, the combined widths of the side walls 120 may be lessthan a diameter of the first metal layer 110, and a plurality of gapsamong a plurality of side walls 120 may be equally located along theperimeter of the first metal layer 110.

The second metal layer 130 may include a thin and flat metal plate andmay include the same conductive metal as the first metal layer 110. Forexample, a thickness of the second metal layer 130 may be in a range ofabout 2 to about 4 μm. In addition, the second metal layer 130 may havethe same circular or regular polygonal (e.g., equilateral) shape as thefirst metal layer 110. A size or diameter of the second metal layer 130may be less than the size or diameter of the first metal layer 110 sothat the second metal layer 130 may be disposed in a space surrounded bythe plurality of side walls 120. As described above, the second metallayer 130 may be suspended on the first metal layer 110 by thesupporting member on the semiconductor substrate 101. The distancebetween the first metal layer 110 and the second metal layer 130 may beslightly less than a height of the side wall 120.

In addition, the second metal layer 130 may include a plurality of ports131 protruding radially from edges of the second metal layer 130, aplurality of slots 132 between the center and each of the vertices ofthe second metal layer 130, and an opening 133 at the center of thesecond metal layer 130. The plurality of ports 131 may receive signalsfrom an oscillator 150 (refer to FIGS. 12A and 12B) to be describedbelow and the signals generated from the oscillator 150 may be providedto the electromagnetic wave radiator 100 via the plurality of ports 131.Each port 131 may extend from the each vertex of the second metal layer130 and may protrude out of the first metal layer 110 through the gapbetween two adjacent side walls 120. Each slot 132 formed by partialpenetration through the second metal layer 130 may be formed to extendin a radial direction between the center and each vertex of the secondmetal layer 130. Electromagnetic waves radiated from the electromagneticwave radiator 100 may be radiated through respective slots 132. Inaddition, the circular opening 133 formed by partial penetration througha central region of the second metal layer 130 may suppress noise. Theelectromagnetic wave radiator 100 may have a radially symmetricstructure, and a cavity for resonating an electromagnetic wave,particularly a millimeter-wave/terahertz (THz)-wave, may be preparedinside a space surrounded by the first metal layer 110, the plurality ofside walls 120, and the second metal layer 130.

FIG. 2 is a perspective view of an electromagnetic wave radiatoraccording to an example embodiment of the present disclosure andillustrates a phase of a signal applied to each port of theelectromagnetic wave radiator. Referring to FIG. 2, an amplificationcircuit 140, which is two-staged, may be between two adjacent ports 131.A plurality of amplification circuits 140 may be arranged between theports 131 of the entire electromagnetic wave radiator 100 in a loopshape. In addition, signals having evenly spaced phases may berespectively applied to the plurality of ports 131 of theelectromagnetic wave radiator 100. In other words, phase differencesbetween the signals applied to the two adjacent ports 131 in theelectromagnetic wave radiator 100 may be all the same. For example, whenthe electromagnetic wave radiator 100 has eight ports 131, a signalhaving a phase of about 0° may be applied to the port 131 at the 12o'clock direction and, in a counter-clockwise direction, signals havingphases of about 45°, about 90°, about 135°, about 180°, about 225°,about 270°, and about 315° may be respectively applied to the ports 131.

Signals having evenly spaced phases applied via the plurality of ports131 may resonate in the cavity defined by the first metal layer 110, theplurality of side walls 120, and the second metal layer 130. In otherwords, the electromagnetic wave radiator 100 may be excited by signalshaving evenly spaced phases applied via the plurality of ports 131.Then, signals applied via the plurality of ports 131 may be combined inthe cavity. The cavity may store a significant amount of electromagneticwave energy by confining the electromagnetic wave therein. Thereafter,the electromagnetic wave corresponding to a resonance frequency may beradiated to the outside via the plurality of slots 132. Theelectromagnetic wave radiator 100 according to the present exampleembodiment may function as a slot antenna, a resonant tank, a powercombining network, as well as a radiator. Thus, since it is notnecessary to use a separate coupling network or an antenna buffer, thesize of the electromagnetic wave radiator 100 may be manufactured to bevery small; thereby downsizing of a millimeter-wave/THz-wave transceivermay be possible.

Since the signals having evenly spaced phases are combined, thecircularly-polarized signal may be radiated from the electromagneticwave radiator 100 according to the present example embodiment. Inaddition, since signals having the evenly spaced phases are radiatedafter having resonated in the cavity, the circularly-polarized signalmay be radiated without leakage in the substrate and consequently,elements such as such as a silicon lens may not be needed. In addition,since the electromagnetic wave is distributed in a large confined areain the cavity, a cavity resonance may improve a quality factor(Q-factor). The quality factor (Q-factor) is a parameter that describeshow underdamped an oscillator or resonator is, and characterizes aresonator's bandwidth relative to its center frequency. As a result,conductive loss may be reduced by lowering the current density of thesignals applied to the electromagnetic wave radiator 100. In addition,low phase noise (or phase noise) and high efficiency oscillation may beachieved by high Q-factors.

FIG. 3 illustrates an equivalent circuit of an electromagnetic waveradiator 100 according to an example embodiment. Referring to FIG. 3,amplification circuits 140 may be arranged in a loop shape between theports 131 of the entire electromagnetic wave radiator 100 and aresonance circuit 141 may be disposed at each port 131. As shown in FIG.3, the electromagnetic wave radiator 100 may have a rotationallysymmetrical cavity structure. Signals applied to the plurality of ports131 of the electromagnetic wave radiator 100 may have the evenly spacedphases like a steady-state oscillation and all the signals may have thesame amplitude. In this configuration, port impedance at all ports 131of the electromagnetic wave radiator 100 may be the same.

FIG. 4 illustrates an equivalent circuit of a resonance circuit at oneport 131 of the electromagnetic wave radiator 100. Values of a coil L, acapacitor C, and a resistor R_(T) in the equivalent circuit, illustratedas an RLC parallel resonance circuit, of FIG. 4 may be determined byvarious factors such as sizes and thicknesses of the first metal layer110, the side wall 120, and the second metal layer 130, and a gapbetween the first metal layer 110 and the second metal layer 130 and alength of the slot 131, and may be appropriately selected in accordancewith an oscillation frequency of the electromagnetic wave radiator 100.For example, when L is about 1.44 pH, C is about 1.31 pF, and R_(T) isabout 40 Ω, the oscillation frequency of the electromagnetic waveradiator 100 may be about 116 GHz.

FIG. 5 illustrates a configuration of the amplification circuit 140connected between two adjacent ports 131 of the electromagnetic waveradiator 100. Referring to FIG. 5, each amplification circuit 140 mayinclude an input matching unit, an inter-stage matching unit, and anoutput matching unit. In addition, a first common-emitter transistor Q1may be disposed between the input matching unit and the inter-stagematching unit, and a second common-emitter transistor Q2 may be disposedbetween the inter-stage matching unit and the output matching unit. Theamplification circuits 140 of the electromagnetic wave radiator 100 maybe formed, for example, on the semiconductor substrate 101 illustratedin FIG. 1.

According to an example embodiment, when gains of the first and secondcommon emitter transistors Q1 and Q2 are respectively A_(V1) and A_(V2),and the first and second common emitter transistors Q1 and Q2 have thesame optimum voltage gain (that is, A_(V1)=A_(V2)=A_(OPT)), oscillationhaving maximum RF power may be achieved. In the case the electromagneticwave radiator 100 has, for example, eight ports 131, the input matchingunit, the inter-stage matching unit, and the output matching unit ineach amplification circuit 140 may be designed to have a phasedifference of π/4. In addition, the input matching unit, the inter-stagematching unit, and the output matching unit in each two-stageamplification circuit 140 may be designed to suppress frequencies otherthan the resonance frequency.

Each of the amplification circuits 140 arranged in a loop shape in theelectromagnetic wave radiator 100 having a rotationally symmetricstructure may have the same port admittance. In addition, each of theport admittances may, for maintaining oscillation, have a negativeresistance that can offset a cavity loading impedance at the resonantfrequency. When a total admittance of the electromagnetic wave radiator100 has a negative real part at the resonance frequency, the maximumoscillation power may be delivered to the cavity.

For example, FIG. 6 is a graph showing frequency responsecharacteristics of a real part and an imaginary part of the totaladmittance of the electromagnetic wave radiator 100. In the graph ofFIG. 6, it is assumed that the electromagnetic wave radiator 100 haseight ports 131, there is a phase difference of π/4 between two adjacentports 131, and the resonant frequency is about 115 GHz. Referring toFIG. 6, at the resonant frequency, the real part of the total admittancemay be less than or equal to about 0 and the imaginary part may be equalto about 0. In addition, the real part of the total admittance isgreater than about 0 at frequencies other than the resonant frequency.

FIG. 7 is a graph showing a measurement result of a polarization patternof an electromagnetic wave radiated from the electromagnetic waveradiator 100 and FIG. 8 is a graph showing a measurement result of aradiation pattern of an electromagnetic wave radiated from theelectromagnetic wave radiator. The graph of FIG. 8 is the resultmeasured in planes having two azimuth angles φ of 0° and 90°. Asillustrated in the graph of FIG. 7, the polarization pattern of theelectromagnetic wave radiated from the electromagnetic wave radiator 100may be circularly-polarized light having an axial ratio better thanabout 0.8 dB. In addition, as illustrated in the graph of FIG. 8, theradiation pattern of the electromagnetic wave radiated from theelectromagnetic wave radiator 100 may have a beam width of about 25° andbe almost symmetrical with respect to a boresight.

FIG. 9 is a graph illustrating a measurement result of spectralcharacteristics of an electromagnetic wave radiated from theelectromagnetic wave radiator 100, and FIG. 10 is a graph illustrating ameasurement result of phase noise characteristics of an electromagneticwave radiated from the electromagnetic wave radiator 100. Referring toFIG. 9, the electromagnetic wave radiated from the electromagnetic waveradiator 100 may have a peak at about 114.1 GHz. At the peak, theequivalent isotropically radiated power (EIRP) may be about 14 dBm, theEIRP/P_(DC) may be about 5%, and the DC-to-RF efficiency may be about3.7%. In addition, referring to FIG. 10, the electromagnetic waveradiator 100 may show phase noise of about −99.3 dBc/Hz@1 MHz offset.This low phase noise may be due to the high Q-factor through the cavityresonance of the electromagnetic wave radiator 100 and the noisereduction due to the power coupling of the ports through the cavity. Inaddition, even when a DC power greatly varies, the resonance frequencymay be varied to less than about 1.3 GHz (about 1%) due to the highQ-factor resonance.

Hereto, the case has been described when the electromagnetic waveradiator 100 includes eight ports 131. However, example embodiments arenot limited thereto. FIGS. 11A through 11 E illustrate various exampleembodiments of the electromagnetic wave radiator 100. Referring to FIG.11A, the electromagnetic wave radiator 100 may have three ports 131. Inthis case, the first metal layer 110 and the second metal layer 130 mayhave a circular or regular triangle shape. In addition, the phasedifference between adjacent ports 131 may be 2π/3. For example, a signalhaving a phase of about 0° may be applied to a port 131 at the 12o'clock direction and signals having phases of 120° and 240° may berespectively applied to ports 131 in a counter-clockwise direction. Inaddition, as illustrated in FIG. 11B, the electromagnetic wave radiator100 may have four ports 131. In this case, the first metal layer 110 andthe second metal layer 130 may have a circular or square shape, and thephase difference between the adjacent ports 131 may be π/2. For example,a signal having a phase of about 0° may be applied to the port 131 atthe 12 o'clock direction and signals having phases of 90°, 180°, 270°may be applied to respective ports 131. In addition, as illustrated inFIGS. 11C to 11E, the electromagnetic wave radiator 100 may have five,six, or eight ports 131. In addition, other numbers of ports 131 (e.g.,seven, nine, ten, etc.) of the electromagnetic wave radiator 100 may beselected as necessary.

FIGS. 12A and 12B illustrate various example embodiments of a connectionrelationship between respective ports 131 and oscillators 150 of theelectromagnetic wave radiator 100. As illustrated in FIG. 12A, theelectromagnetic wave radiator 100 may include a plurality of oscillators150 a, 150 b, and 150 c, which are respectively connected to a pluralityof ports 131 a, 131 b, and 131 c. For example, when the electromagneticwave radiator 100 has three ports 131 a, 131 b, and 131 c, theelectromagnetic wave radiator 100 may include three oscillators 150 a,150 b, and 150 c. In this case, the first oscillator 150 a connected tothe first port 131 a may provide a signal having a phase of about 0°,and the second oscillator 150 b connected to the second port 131 b mayprovide a phase of about 120°, and a third oscillator 150 c connected tothe third port 131 c may provide a signal having a phase of about 240°.The first through third oscillators 150 a, 150 b and 150 c may be formedon the semiconductor substrate 101 illustrated in FIG. 1.

In addition, referring to FIG. 12B, the electromagnetic wave radiator100 may include only one oscillator 150 connected to the plurality ofports 131 a, 131 b, and 131 c. One oscillator 150 can supply signals toeach of the plurality of ports 131 a, 131 b, and 131 c via a first wire151 a, a second wire 151 b, and a third wire 151 c. In this case, phasesof signals applied to the plurality of ports 131 a, 131 b, and 131 c maybe adequately delayed by adjusting electrical lengths of the firstthrough third wires 151 a through 151 c. That is, the first throughthird wires 151 a through 151 c may have electrical lengths that providedifferent phase delays from each other. For example, when theelectromagnetic wave radiator 100 has three ports 131 a, 131 b, and 131c, the electrical length of the second wire 151 b connected to thesecond port 131 b may be selected so as to have a phase delay of about120° with respect to the first wire 151 a. Likewise, the electricallength of the third wire 151 c connected to the third port 131 c may beselected so as to have a phase delay of 120° with respect to the secondlead 151 b connected to the second port 131 b.

FIG. 13 illustrates an electromagnetic wave radiator array according toanother example embodiment. Referring to FIG. 13, the electromagneticwave radiator array 200 may include a plurality of two-dimensionallyarranged electromagnetic wave radiators 100. The electromagnetic waveradiator array 200 may increase the overall power of the radiatedmillimeter-wave/THz-wave by using multiple electromagnetic waveradiators 100. In addition, the direction of a main lobe of themillimeter-wave/THz-wave may be adjusted via a beam steering technology.For example, when the phases of signals applied to a plurality of ports131 a through 131 h are the same for all electromagnetic wave radiators100 in the electromagnetic wave radiator array 200, themillimeter-wave/THz-wave may travel toward the front of theelectromagnetic wave radiator array 200. For example, a signal having aphase of about 0° is applied to the first port 131 a , a signal having aphase of about 45° is applied to the second port 131 b, a signal havinga phase of about 90° is applied to the port 131 c, a signal having aphase of about 135° is applied to the fourth port 131 d, a signal havinga phase of about 180° is applied to the fifth port 131 e, a signalhaving a phase of about 225° is applied to the sixth port 131 f, asignal having a phase of about 270° is applied to the seventh port 131g, and a phase of about 315° is applied to the eighth port 131 h, of allthe electromagnetic wave radiators 100, the millimeter-wave/THz-wave maytravel toward the front of the electromagnetic wave radiator array 200.

In addition, when the phase of the signal is slightly changed for eachcorresponding port of the plurality of electromagnetic wave radiators100, a traveling direction of the millimeter-wave/THz wave may bechanged to the right or left side or the up or down direction. Forexample, in FIG. 13, a signal having a phase of about 0° is applied tothe first port 131 a of the electromagnetic wave radiators 100 arrangedon a first column from a left side, a signal having a phase of about 10°is applied to the first port 131 a of the electromagnetic wave radiators100 arranged on a second column from the left side, and a signal havinga phase of about 20° is applied to the first port 131 a of theelectromagnetic wave radiators 100 arranged on a third column from theleft side. In this case, signals having phases of about 55°, about 100°,about 145°, about 190°, about 235°, about 280°, and about 325° may berespectively applied to the second through eighth ports 131 b through131 h of the electromagnetic wave radiators 100 arranged on the secondcolumn from the left side. In addition, signals having phases of about65°, about 110°, about 155°, about 200°, about 245°, about 290°, andabout 335° may be respectively applied to the second through eighthports 131 b through 131 h of the electromagnetic wave radiators 100arranged on the third column from the left side. Then, themillimeter-wave/THz-wave may have a tilted wave front when viewed towardthe drawing and then, travel in the right direction.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exampleembodiment should typically be considered as available for other similarfeatures or aspects in other example embodiments.

While one or more example embodiments have been described with referenceto the figures, it will be understood by those of ordinary skill in theart that various changes in form and details may be made therein withoutdeparting from the spirit and scope as defined by the following claims.

What is claimed is:
 1. An electromagnetic wave radiator comprising: afirst metal layer; a plurality of metal side walls vertically protrudingalong an edge of the first metal layer; and a second metal layersuspended over the first metal layer, wherein the second metal layercomprises a plurality of ports extending radially from edges of thesecond metal layer and a plurality of slots penetrating the second metallayer in a radial direction.
 2. The electromagnetic wave radiator ofclaim 1, wherein every pair of adjacent metal side walls of theplurality of metal side walls is spaced apart from each other, and eachport of the plurality of ports is disposed to pass through a gap betweena corresponding pair of adjacent metal side walls.
 3. Theelectromagnetic wave radiator of claim 1, wherein the first metal layerand the second metal layer have an identical regular polygonal shape,wherein each metal side wall of the plurality of metal side walls isdisposed perpendicular to an upper surface of the first metal layer atthe edge of one side of the identical regular polygonal shape of thefirst metal layer, wherein a first length of the each metal side wall ofthe plurality of metal side walls is less than a second length of theone side of the first metal layer, and wherein a gap between twoadjacent metal side walls is disposed at a vertex of the identicalregular polygonal shape of the first metal layer.
 4. The electromagneticwave radiator of claim 3, wherein the plurality of ports radiallyprotrude from respective vertices of the identical regular polygonalshape of the second metal layer, and the plurality of slots are disposedbetween a center of the second metal layer and the respective verticesof the identical regular polygonal shape of the second metal layer. 5.The electromagnetic wave radiator of claim 1, wherein the first metallayer and the second metal layer have an identical circular shape,wherein each metal side wall of the plurality of metal side walls isdisposed perpendicular to an upper surface of the first metal layer atthe edge of the first metal layer, wherein the edge of the first metallayer corresponds to a perimeter of the identical circular shape of thefirst metal layer, wherein a combined length of the plurality of metalside walls is less than a diameter of the identical circular shape ofthe first metal layer, and wherein a plurality of gaps between theplurality of metal side walls are disposed at regular intervals alongthe perimeter of the identical circular shape of the first metal layer.6. The electromagnetic wave radiator of claim 5, wherein each of theplurality of ports protrudes in the radial direction of the second metallayer between the plurality of gaps between the plurality of metal sidewalls.
 7. The electromagnetic wave radiator of claim 1, wherein thesecond metal layer is disposed in a space surrounded by the plurality ofmetal side walls.
 8. The electromagnetic wave radiator of claim 1,wherein the second metal layer further comprises an opening penetratingthrough a central region of the second metal layer.
 9. Theelectromagnetic wave radiator of claim 1, further comprising at leastone oscillator configured to provide a signal to each of the pluralityof ports, wherein the at least one oscillator is configured so thatsignals provided to the plurality of ports have an identical amplitudeand different phases from each other, and phase differences betweensignals applied to two adjacent ports are identical.
 10. Theelectromagnetic wave radiator of claim 9, wherein the second metal layerhas n ports, and a phase of the signal applied to the an m-th port is2m/πn, where n is a natural number and m is 0, 1, . . . , n−1.
 11. Theelectromagnetic wave radiator of claim 9, wherein the at least oneoscillator is connected to the plurality of ports in a one-to-onemanner.
 12. The electromagnetic wave radiator of claim 9, wherein oneoscillator of the at least one oscillator is connected to the pluralityof ports via a plurality of wires and each of the plurality of wires hasan electrical length providing a different phase delay from each other.13. The electromagnetic wave radiator of claim 1, wherein a spacesurrounded by the first metal layer, the plurality of metal side walls,and the second metal layer defines a cavity for resonance of anelectromagnetic wave, and the first metal layer, the plurality of metalside walls, and the second metal layer are configured so that the cavityfunctions as a resonator, a power combiner, and a radiator.
 14. Theelectromagnetic wave radiator of claim 1, further comprising a pluralityof amplification circuits between two adjacent ports of the plurality ofports, wherein the plurality of amplification circuits are disposed in aloop shape between the plurality of ports.
 15. The electromagnetic waveradiator of claim 14, each of the plurality of amplification circuitscomprises an input matching unit, an inter-stage matching unit, anoutput matching unit, a first common emitter transistor between theinput matching unit and the inter-stage matching unit, and a secondcommon emitter transistor between the inter-stage matching unit and theoutput matching unit.
 16. The electromagnetic wave radiator of claim 15,wherein the first common emitter transistor and the second commonemitter transistor have an identical voltage gain.
 17. Theelectromagnetic wave radiator of claim 14, port impedances for theplurality of ports are identical to each other, and port admittances forthe plurality of ports are identical to each other.
 18. Theelectromagnetic wave radiator of claim 17, each of the port admittanceshas a negative resistance offsetting a cavity load impedance at aresonant frequency, and a total admittance of the electromagnetic waveradiator has a negative real part at the resonant frequency.
 19. Theelectromagnetic wave radiator of claim 1, wherein the electromagneticwave radiator is configured to radiate a circularly-polarizedmillimeter-wave/terahertz (THz) wave.
 20. An electromagnetic waveradiator array comprising a plurality of two-dimensionally arrangedelectromagnetic wave radiators, wherein each electromagnetic waveradiator of the plurality of two-dimensionally arranged electromagneticwave radiators comprises: a first metal layer; a plurality of metal sidewalls vertically protruding along an edge of the first metal layer; anda second metal layer suspended over the first metal layer, wherein thesecond metal layer comprises a plurality of ports radially extendingfrom the edge of the second metal layer and a plurality of slotspenetrating the second metal layer in a radial direction.